One of the shortcomings of a traditional pump shotgun is low ammo capacity and reloads are typically slow. The standard Mossberg 500 has a magazine tube that holds five rounds in the tube and one in the chamber. That is a total of 6 rounds. Due to the design of the Mossberg 500, you cannot add a magazine extension tube. Even if you could, reloading the Mossberg is not a fast endeavor. There are shell manipulations that one can do such as TWINS or QUAD loading. Those types of manipulations take skill and practice but they do work. There is another way to overcome capacity limits and decrease load times, though — by converting it to a box magazine-fed shotgun.
Magazine-Fed Shotgun Conversion Kits
Adaptive Tactical has brought this feature to us in the form of a conversion kit for the Mossberg 500. It will also work with Mossberg 590 and Maverick 88 shotguns. The conversion kit only works with Mossbergs because the factory magazine tube can be unscrewed from the receiver. If you are interested in this make sure you have a five-round mag tube, Mossberg Persuaders usually have a longer magazine tube of about seven rounds. While you could still remove the magazine tube, the Persuader barrel would not work with the Sidewinder Venom Kit.
There are a few different kits. I got the Venom-SE 10 Rnd Box Kit Shotgun Magazine Conversion Kit with 10 Rnd. Box Mag, Wraptor Forend and EX Performance M4 Style Stock.
The installation of the Sidewinder venom kit was straight forward. There is a bit of concern due to how the magazine well lines up with the receiver. Luckily mine lined up pretty well. When I screwed it in all the way, the new tube bottomed out with the mag well just past 6 O’clock position relative to the receiver. So I just backed the tube out just a smidgen.
The Wraptor handle does offer more mounting solutions for accessories. The top rail does allow you to mount a small red dot. However, I caution our readers. It will work but there is a lot of rotational movement in the forend and that means your dot will move left and right so it will throw your zero off. The rail sits high enough that you can still aim with the factory bead sight. In the photo below you can see the Wraptor handle. My Mossberg is a Roadblocker version and that is why it has the gigantic muzzle brake.
I like the HFG since it is closer to me. If you look at the forend in the photo above, you will see a big handstop. That is to protect your hand from being pinched by the mag well when the pump grip moves back.
The magazines come in 5rd and 10-rd box mags. Or they come in a 10-rd rotary drum magazine.
About the Magazines
The magazines a bit bulky though. They are almost twice as wide as a .308 AR magazine. So they do not fit in mag pouches unless you made a custom pouch to fit these. The other problem is the shell stop. These magazines are not your traditional magazine. They do not have feed lips. There is a shell stop that keeps the shells inside the magazine from flying out. Once you insert the magazine into the Sidewinder mag well, the shell stop is pushed out of the way. The shells are then pushed up into the mag tube of the shotgun. Then when you pump back, the pump handle pushes a push rod to push the shell back into the shell lifter. Due to this system, traditional magazines will not work. Also if you have a malfunction and need to remove the magazine, the shell that is in the mag tube will fall out and you lose a round.
EX Performance M4 Style Stock
The M4 style stock is nice but a bit of a pain to install. The bolt that screws into the receiver is recessed all the way into the buffer tube of the MF stock. This required a ridiculously long extension with a couple of adapters and a handle to reach the bolt and screw the stock onto the receiver.
The stock is comfortable even though the grip is very wide and the length-of-pull adjustment is nice for shorter shooters. The crucial issue that causes me to not like M4 style stocks is the use of a pistol grip on a Mossberg 500 — this is not a fault in Adaptive Tactical’s design. It is very difficult to almost impossible to activate the pump release button or the safety while keeping your hand on the pistol grip. So this is a compromise while running this magazine-fed shotgun setup. You will have to shift your grip to switch the safety or the pump release button.
The Sidewinder kit is a unique modification that you can do at home to your Mossberg 500 to make it a magazine-fed shotgun. However, it leaves much to be desired. It is fine as a range toy but reliability is compromised and it is not good to have issues in a home defense shotgun. The kit starts at $199 for the basic Vemon kit with a 5-rd box mag. And you can go all the way with the new handle, stock and 10-rd drum mag for $339. They do come dipped in camo and that is another charge. For more information check out Adaptivetactical.com.